Artemisinin-based combination therapies (ACTs) play an essential role in the current malaria control and elimination campaign. However, the circulation of counterfeit and substandard artemisinins greatly threatens the malaria control efforts. Fake artemisinins containing no or little active ingredients are life-threatening, while substandard drugs encourage resistance development. The scale of this 'lethal problem' is particularly huge in some Southeast Asian countries, where as much as 64% of the artesunate sold on the market was fake. To prolong the life span of artemisinin drugs for treating malaria, strict drug quality control needs to be implemented in these nations. For this purpose, fast and reliable methods of artemisinin detection and quantitation are needed. Traditional methods for quantitation of artemisinins often require expensive instruments and substantial technical support, whereas the rapid qualitative method for screening of fake artemisinin derivatives is less sensitive and variable. Based on our recent success of developing a highly sensitive and reliable enzyme-linked immunosorbent assay (ELISA) using a specific monoclonal antibody against artemisinins, we propose to 1) develop a series of monoclonal antibodies with specificities for the major artemisinin derivatives (dihydroartemisinin, artemether, arteether, and artesunate) using an innovative design of immunogens, 2) develop and optimize an ELISA for accurate quantification of artemisinins, and a lateral flow dipstick assay for rapid, semi-quantitative analysis of artemisinins in antimalarial drugs, 3) perform systematic field surveys of the drug quality of artemisinin-based antimalarial medicines in three Southeast Asian countries using these new tools, and 4) optimize the ELISA conditions so that it can be used as an alternative tool for quantification of artemisinins and its derivatives in pharmacokinetic studies. These immunoassays will offer convenient tools for both accurate quantification of artemisinins and rapid detection of counterfeit and substandard artemisinin derivative drugs, contributing to antimalarial drug quality control.